It's been a big week for chameleons. On Tuesday, scientists announced they'd worked out the secret to the cross-eyed lizard's color changing skin. A day later came the announcement that we'd replicated the skin artificially.
Chameleons are among the select few organisms that are able to change their color at will. There are many different reasons color-changing has evolved in nature, from camouflage to predation to attracting a mate. But most rely on a similar principle: Tuning nanoscale structures to bend and reflect light in different ways.
The chameleon's color-changing trick is actually quite simple. A layer of skin cells contains nanocrystals which reflect light at wavelengths related to their spacing. When the chameleon's skin is relaxed, it takes on one color. When it stretches, the nanocrystals spread outandthe color changes. That discovery was reported earlier this week in Nature Communications.
Now a synthetic color changing materialdescribed this week the journal Opticatakes a page from the chameleon's book, using nanoscale structural features to reflect select colors of light. Basically, tiny rows of ridges are etched onto a silicon film a thousand times thinner than a human hair. Each of these ridges reflects a very specific wavelength of light. By altering the spacing between the ridges, it's possible to finely tune the wavelength of light reflected. That means, like chameleon skin, this material's color changes when stretched.
A fully transparent solar cell that could make every window and screen a power source
Researchers at Michigan State University have created a fully transparent solar concentrator, which could turn any window or sheet of glass (like your smartphone’s screen) into a photovoltaic solar cell. Unlike other “transparent” solar cells that we’ve reported on in the past, this one really is transparent, as you can see in the photos throughout this story. According to Richard Lunt, who led the research, the team are confident that the transparent solar panels can be efficiently deployed in a wide range of settings, from “tall buildings with lots of windows or any kind of mobile device that demands high aesthetic quality like a phone or e-reader.”
Scientifically, a transparent solar panel is something of an oxymoron. Solar cells, specifically the photovoltaic kind, make energy by absorbing photons (sunlight) and converting them into electrons (electricity). If a material is transparent, however, by definition it means that all of the light passes through the medium to strike the back of your eye. This is why previous transparent solar cells have actually only been partially transparent — and, to add insult to injury, they usually they cast a colorful shadow too.
To get around this limitation, the Michigan State researchers use a slightly different technique for gathering sunlight. Instead of trying to create a transparent photovoltaic cell (which is nigh impossible), they use a transparent luminescent solar concentrator (TLSC). The TLSC consists of organic salts that absorb specific non-visible wavelengths of ultraviolet and infrared light, which they then luminesce (glow) as another wavelength of infrared light (also non-visible). This emitted infrared light is guided to the edge of plastic, where thin strips of conventional photovoltaic solar cell convert it into electricity. [Research paper: DOI: 10.1002/adom.201400103 - "Near-Infrared Harvesting Transparent Luminescent Solar Concentrators"]
If you look closely, you can see a couple of black strips along the edges of plastic block. Otherwise, though, the active organic material — and thus the bulk of the solar panel — is highly transparent. (Read: Solar singlet fission bends the laws of physics to boost solar power efficiency by 30%.)
Michigan’s TLSC currently has an efficiency of around 1%, but they think 5% should be possible. Non-transparent luminescent concentrators (which bathe the room in colorful light) max out at around 7%. On their own these aren’t huge figures, but on a larger scale — every window in a house or office block — the numbers quickly add up. Likewise, while we’re probably not talking about a technology that can keep your smartphone or tablet running indefinitely, replacing your device’s display with a TLSC could net you a few more minutes or hours of usage on a single battery charge.
The researchers are confident that the technology can be scaled all the way from large industrial and commercial applications, down to consumer devices, while remaining “affordable.” So far, one of the larger barriers to large-scale adoption of solar power is the intrusive and ugly nature of solar panels — obviously, if we can produce large amounts of solar power from sheets of glass and plastic that look like normal sheets of glass and plastic, then that would be big.
In a trial involving mice, an international team of researchers used microscopic "nanoneedles" to coax the body into generating new blood vessels. Applied to humans, the technology could eventually be used to get organs and nerves to repair themselves.
Researchers from Imperial College London and the Houston Methodist Research Institute used the nanoneedles to deliver nucleic acids the building blocks of all living organisms and transmitters of genetic information to a specified area. Once delivered to a cell or tissue, the nucleic acids do their work by regenerating lost function. The researchers, a team led by Ciro Chiappini and Molly Stevens from the Imperial College London, describe their findings in the latest issue of Nature Materials.
In the case of the current study, DNA and siRNA nucleic acids were successfully delivered to human cells in the lab. Also, the researchers were able to facilitate a six-fold increase in the formation of new blood vessels in the back muscles of mice. The technique, conducted over a two-week period, didn't cause any inflammation or other harmful side effects.
Acting like sponges, the porous nanoneedles which are 1,000 times smaller than a human hair can pack considerably more nucleic acids than solid structures. They work by bypassing the outer membrane of a cell, piercing it to deliver the nucleic acids. Notably, it does so without harming or killing the cell. By accessing a cell's cytoplasm directly, the researchers were able to efficiently reprogram it.
And because the nanoneedles are made from biodegradable silicon, they can be left in the body and not leave a toxic residue; they dissolve in about two days, leaving a negligible trace of harmless orthosilicic acid.
The nanoneedles have not been tested on humans, but the work on mice looks promising. Eventually, they could be used to restore lost function in tissues and organs, or used during organ transplants for an added boost as the organs settle into their new environment.
Conceivably, they could also be incorporated into a flexible bandage. For example, when applied to severely burnt skin they could reprogram the cells to heal the injury with functional tissue instead of forming a scar.
Antiperspirants reduce perspiration and deodorants conceal its associated smells, but a new perfume developed by researchers at Queen's University Belfast uses sweat to its advantage, releasing pleasant aromas when it comes into contact with moisture and trapping molecules responsible for BO.
The researchers call their creation a "pro-fragrance ionic liquid with stable hemiacetal motifs." It sounds complicated, but it's pretty straightforward, conceptually. "Ionic liquid" is the fancy name for a salt that exists in a liquid state, in this case at around room temperature. When a fragrant alcohol is added to the liquid, the two form a hemiacetal. In the hemiacetal state, the compound is actually odorless. But when the compound is exposed to water (say, the moisture in your perspiration), a hydrogen molecule takes the place of the fragrant alcohol, freeing up the latter to do its job, i.e. smell good. Researchers H.Q. Nimal Gunaratne, Peter Nockemann, and Kenneth Seddon, all of Queen's University Ionic Liquid Laboratories (QUILL), describe their creation in greater detail in the journal Chemical Communications, but this figure summarizes things nicely:
As an added benefit, the ionic liquid attracts thiols, the compounds in sweat responsible for its odor. So this "perfume release system," as the researchers call it, is actually working double duty, releasing pleasant smells and trapping bad ones simultaneously.
According to a press release from University Belfast, the researchers are looking to tap into the personal care industry and are working with a "perfume development company," which isn't exactly surprising. But Gunaratne says he thinks the system "could also be used in others area of science, such as the slow release of certain substances of interest." Therapeutic substances, perhaps? (What do you call the disease where rainbows erupt from your armpits every time you lift your hands over your head?)
Nice. Really hope this pans out. Got to try and be healthy to live long enough for whatever new awesome things scientists discover.
Bug guts on your windshield are an inevitable part of life and a reminder of your own fleeting mortality. But theyre also a major drag on the aerodynamics of a car or planereducing the fuel efficiency of airplanes as much as a whopping six percent, according to NASA.
Thats a major difference in cost, and could amount to millions when tallied across an entire fleet. Thats why, for the past few years, NASA has been working on a chemical coating that could prevent bug guts from getting stuck on the wings of planes and creating unnecessary drag. Though NASA first published a paper on the topic in 2013, its now testing five different coatings on a Boeing 757 to find out whether they work.
The name of the project sounds deceptively bureaucratic: Insect Accretion and Mitigation. It turns out that keeping bugs from getting stuck on planes is actually kind of a tough problemone thats plagued the aviation industry for decades. The problem isnt just about creating a hydrophobic surface. The guts themselves are what create the problem, NASA explained a few years ago:
Its not just water you have to deal with. Yes, theres a lot of water in a bug, but theres also some biological components that actually impart the stickiness, and we have to deal with preventing those from sticking even though we know how to prevent water from sticking, [Mia Siochi, of the Advanced Materials and Processing Branch at Langley] said.
At Langley, the team says it uses something called a bug gun (use your imagination) to shoot bugs at test subjects in a wind tunnel at speeds of 150mph. Oh, youd like to see a schematic of this gun? Here you go, courtesy of the study Engineered Surfaces for Mitigation of Insect Residue Adhesion:
Suffice to say, the upcoming tests out in the wild are the result of years of testing and research. Last week, NASA announced it would be running a series of experiments on a 757 that its testing a number of other efficiency-oriented design changes on. To create a control group, itll measure how many bugs accumulate on the un-coated wings. Then, itll install five coated panels on the wings to see how they differ.
In the 2013 study, they counted incidences of adhesion a bit like a detective counts bullet holes:
Only one question about their methodology remains. How did they pick where to test the coatings? NASAs Kathy Barnstorff writes that the team looked for the best bug-infested area in which to flight test the surfaces, looking at 90 different airports. Out of all the bug-clogged runways in America, which provided the most splatter-y conditions? Shreveport.
